Thread grinding machine



March 18, 1947. s. STEWART ET Al. 2,417,714-

THREAD GRINDING MACHINE Filed July 17, 1943 11 Shuats-$hut i [anemic/ash 8 Qlzberfi Sieuxari Guenfker Brzkkmann Harald 4V2 figferdh m-rrasuga-as Q March 18, 1947. e. STEWART ETAL 2,417,714

THREAD GRINDING MACHINE li werdors Gilerf Sfewar Guenlzer BrinbnazmHarold M Sfzyferih ,ax 02 44 49.? MAJ-.

jlwbma-m March18, 1947. @STEWART ETAL 2,417,714

THREAD GRINDING MACHINE Filed July 17, 1943 11 Shats-Sheet 3 Q Q W L 3 nN n I at a Q 0 g is r Q? 3 i N T I 9 rm 'm 1% Q a a m a I Q n l w I s aT I E =0 w 5 5'3 53 .5: 3 i S I EN g 'o i ,3, 3: 2 Q a jizaezzfora P3 9Gilbert Steam/e15 3 uenfberfi'inkmann March 18, 1947. STEW RT ET AL2,417,714

THREAD GRINDING MACHINE Filed July 17, 1943 11 Sheets-Sheet 4 GilberiSiewarf Guexzilzer Brz'rzkmarm HaroZZ fl LS yferh- March 18, 1947. 'G.STEWARTETAL "minim x mmnme momma Filed July 17, 1943 r 11 Sheets-Sheet 5March 18, 1947 STEWART g- 2,417,714

"rams/m GRINDING VIACH'INE Filed Jul 17. 1943 11 Sheets-Shoot 'r [ravenfans Gilbert Stewart Gus/tiller Brinkmaan Harold Ms yferflz I wronqgpasMan-ch18,- 1947. G. STEWART ETAL 2,417,714

' THREAD amunme momma FilQ-July 17. 1945 11 Shasta-Sheet a In uniorsGizber Stewari GuenJ/zer Pinkman/z Harold M-Sgferih PW OTTO QLE-m s,"STEWART. ET AL 2,417,714

THREAD GRINDING MACHINE Filed July 17, 1943 11 Sheets-Sheet 9 March 18,1947. e. STEWART ETAL 1 4 7 THREAD GRINDING MACHINE Filad July 17. 194311 Sheets-Sheet 1o [rzzneazzzlora Gilber 66ewar Glue/like! BrzhkmannCATTOWJ v mean M n a. 1947 a UNIT STATES, PAT

p \GilbertTStewart.and"Guentherlirinkmann.

i troit, and liaroldjN. Seyferth,1 East Detroit,

I Mich assignors to Ex Cell-0 Corporation, De-

. troit, Micla, a cerporation ofM ichigan Application-July 17, 1943,Serial No. 495,162

recla ms. (01. 515-95 The present invention relates toima chine tools;and has particularyreference to thread grinding machines. q

One of the objects of the inventionisi toprovide a novel thread grindingmachine which may be operated with an automatic cycle, andg whichembodies. a simp1ifled and comparatively inexpensive. structure foreffecting wheel feed, dresser feed, wheel retraction and advance,andtaper adjustment. f5;

A more specific o bject is toprovide a new and improved thread grindingmachine inwhich an .valve panel forming part of a hydrau1icidrivestant-ially alongline, e-sor Fig. 4.

Fig. 515a fragmentary plan viewtaken sub .Figgs is a detailverticalsectionalview taken. substantially-alongline 8-- 6of Fig. 4.view of the cross feed anddresser teed mecha Fig. 7 afragm ntaryhorizontal sectional nisms.

Fig. 8is' aliragmentary longitudinal vertical sectional, view of thedresser ieed mechanism.

Fig. 9is afragmentary plan view of a control transmission for theworktable and spindle.

movements of the grinding" wheel are effected? through. a single wheel.slide, and in which wheel retractionand' advance and taper adjustmentare imparted through an actuating linkage to "the wheel slide withoutment. 1

Anothen object is to provide a novel thread grinding machine having a'cOmbined hydraulic and mechanical drive for rotating and translat-' ingthe work spindle in timed relation and in which the drive is subjecttoselectivefspeed variation at different points in the rnachine cycle."for example, to vary the speed selectively tor a series ofrough grindingpasses; over the thread altering the infeed adjustproper, one finishgrinding pass over the thread Other cbjectsand advantages willbecome'ap-40 parent as. thedescription proceeds.

In the, accompanyingldrawings,

Figure l. is a front perspective view of grinding machine invention:

[with a Fig. 2 is a rearperspectiireview of themachinei Fig. 3 is afragmentary transverse vertical sectional view of thecross feedmechanism of the machine.

Fig. 4 is a fragmentar ammothint V of the crossfeedmechanism.

view of. the work spindle head.

tend ,tolimitthe inventiontothe specific form mbodying the features ofour" Fig, 10 is a side elevational view of the control valve panel shownin Fig a. h

Fig. 11 is a transverse vertical sectional view of; the valve panel.taken along line lI-ii of Fig.110.x

is a vertical sectional view through the valvepanel taken along linei2--i2 of Fig. 11." J 1 Fig. 13 is a diagrammatic representation of thehydraulic transmission and control circuits for thework table andspindle drives. l

- Fig. 14 is a diagrammatic.representation oi th hydraulic transmissionand control circuits for the entiremachine.

Fig. 15 is a diagrammaticrepresentation oi the mechanicaiand hydraulicdrives of themachine.

.Fig. .16 is a diagrammatic representation 01 I the electric control(-ircuitsfor the machine.

Figi 1.71s a fragmentary longitudinal sectional Whilefthe invention issusceptible oi various modiflcationsfiand alternative constructions, wehave shown in the drawings and will hereindescribe in detail thepreferred embodiment, but it is to be understeod that we do not therebyindisclosed.ybut intend to cover all modifications and, alternative.constructions falling within the spirit and scope oithe invention asexpressed in the appended claims.

Referring more particularly to thefdrawings, the machine constitutingthe exemplary embodi merit of the invention'is adapted for grindingscrew threads on various types andtorms of workpieces, and in thepresent instance a work blank W. of an aircraft engine cylinder barrelis shown. I

The machine comprises an elongated horizon tally disposed main base Iformed on the top".

E NT omcs reciprocatory work table 3, and having a rearward extension 4formed with a set of transverse ways 5 for supporting a tool head 6, Arotary tool spindle 1 is mounted in the tool head 6 for rotation on anaxis extending generally longitudinally of the table 3, and supports asuitable grinding wheel G.

A headstock or work head 8, and a suitable tailstock 9, are mounted inlongitudinally spaced relation on thevtable 3 for reciprocationtherewith. Journaled in the headstock '8 is a work spindle l having achuck II in which one end of the work blank W is secured for rotarydrive. The other end of the blank is'rotatably supported by thetailstock 9. mechanical drive transmission is provided for translatingthe table 3 and rotating the work spindle In in timed relation and inforward and reverse directions at different selective speeds;

Thus, the work blank W is adapted for rotation and translation axiallythrough cutting engage-.-

ment with the rinding wheel G in timed relation to the rotation asdetermined by the lead of the thread orthreads to be ground.

The tool 6 is shiftable transversely of the work spindle 10 eitherforwardly to locate the grind-" in'g' wheel G in operative grindingposition, or rearwardly to locate the wheel inidle or retractedposition. A cross feed mechanism 12 is provided for automatically'adJustingthe operative grinding position of the wheel G step-by-step intimed relation to the successive working passes of the work spindle l0until the blank W has been ground to final size. The shifting of thetool head 6 is effected by a retract mechanism l3 which isautomaticallyoperable to separate'the grinding wheel G laterally from the blank W foreach rapid traverse return'movement of the table 3 without changing thesetting 'ofthe cross feed mechanism. A taper mechanism I4 is optionallyavailable for automatically superim posing ataper adjustment .on theinfeed position of thegrindin Wheel G in timedrelation to thelongitudinal traverse of the table 3 'as-determined by the form ordegree of taper desired on the work.

Mounted on the tool head 6 atthe rear of the grinding wheel G is asuitable dressing mechanism l for dressing or truing the grindingsurface. The dressing mechanism 15 is automatically operable at selectedtimes in'the machine cycle, and in each operation serves to effect adresserfeed'ofthe dressing tool or tools toward the grinding wheel, andsimultaneously a compensating feed of the tool head 6 toward the axis ofthe work spindle i0 so as to compensate for the reduction in diameter ofthe grinding wheel G. v i The operation of the machine is controlled bya combined hydraulic and electridsystem in which the movements of themain'units are interlocked and timed, and which is selectivelyadjustable to obtain different automatic machine cycles. In oneillustrative cycle, adapted for grinding the threads on aircraft'enginecylinder barrels. the work table 3 is reciprocated a predeterminednumber of times, each reciprocation consisting of aforward grinding passat a relatively slow speed and a return stroke at a rapid traversespeed. For example, there may be five roughing passes at a fast grindingspeed and a final or finishing pass at a slow grinding speed. At the endof each roughing and finishing pass, the grinding speed isredu'c'edduring A combined hydraulic and the final work spindle revolution orpreselected portion thereof if the incomplete thread convolution on theleading end of the work blank is to be removed. The spindle I0 i alwaysrotated in timed relation to the table traverse, and is reversed uponeach reversal of the table. At the,

ment into retracted position after any desired number of grindingpasses, for example after the first and third roughing passes, and againafter the fifth roughing pass before the final or finishing pass. Ineach dressing operation, the dressing cycle is initiated at the start ofthe retract movement of the tool head 6, and continues during thefollowing free return movement of the work head 8, and if necessary thetable 3 will dwell at the end of the return movement topermit completionof the cycle. The dressing cycle comprises a feed of the dressingmechanism l5 toward thegr-inding wheel G, a compensating feed ofthewheel G toward the work axis, and truingof the grindin surface to thedepth of the dresser feed. During the dressing operation, the grindingwheel G preferably is driven at a reduced speed. I I

The work head i The workhead 8 per se forms no part of the presentinvention, and therefore is not-described in full detail. The mechanicaldrive transmission within thework head 8 for the table 3 and spindle I0is generally. similar to that shown in a copending application forUnited States Letters Patent by Guenther Brinkmann, Serial No. 435,-224,. filed March 18, 1942 (now Patent No. 2,389,- 590, issued November27, 1945), and comprises a screw shaft 16 geared .to the spindle I0, andconnected through a meshing worm l1 and worm wheel 18 to an inlet shaftl9 extending to the rear of the head 8 for connection to a suitablesource of power. The wheel 18 is slidably splined to the shaft l6 so asto permit relative axial movementof the latter, and is itselfconstrained against axial movement by bearing lugs |8a at opposite sidesrigidly supported within the head. A lead screw Men the shaft l6 engagesa nut 2| fixed in relation to the machine base I to complate the drivefor the table traverse. Upon rotationof the power inlet shaft IS, thework spindle I 0 and the lead screw 20 are driven in positively timedrelation to rotate and translate the workpiece Win accordance with thethread lead to be ground thereonin forward and reverse directions. I Alead pick-up mechanism, operable by means of a hand wheel 22 at thefront of the machine, is provided for adjusting the position oftranslation of the table 3 relative to the position of rotation of thework spindle I0, as required to locate the work thread in properposition for en agement by the grinding wheel G.

Backlash compensating means likewise is provided for automaticallyadjusting the position of translation of the table 3 relative to theposition of rotation of the spindle ID in one direction or the other tothe extent of the backlash in the drive upon each reversal of the leadscrew 20, i

so as to maintain the work thread in proper relation tothe grindingwheel G in both directions of table translation. In the presentinstance,

the backlash compensating means comprises a. I

hydraulic actuator 23 (Fig'l) which is reversible upon each reversal ofthe work table 3to adjust the drive connection through a predeterminedadjustable distance required to compensate for backlash. The actuator 23comprises a piston 24 reciprocable in a cylinder 25 having fluid supplylines 2 6 and 21 opening to opposite ends and connected to a controlvalve 28 form- 1 ing part oi the main valve panel 28. The valve 28 is ofthe two-position type, and is adapted for. operation by two solenoidsSVCR'Iand SVCL:

in the electric control circuits for themachine. During the forwarddrive tothe right, thesoleconnected in the hydraulic transmission systemdepending on the adjustments of the valves 39 and 48 to receive fluiddischarging from the actuator 32, and to build upa back pressure whichis reflected in the inlet side or the system to control the pressure inthe pump control line 46; and therethrough to vary the output of thepump" in accordance with the fluid. requirements at different times. inthe machine cycle;

The valves 39 and 48 and the restricted adjustable orifices 52 to 55 areincorporated in a unitary valve panel 51 mounted in the front of themachine base I. The panel 51 consists of a rectangular blockiFigs. l1and 12) suitably supported on the base at the front of the machine, andformed withcored passages connected- 4 48 and 56; and other coredpassages defining the w noid SVCR is energized to actuate the valve 28into one end position in which the cylinder lines 26 and 21 areconnected ,respectively to fluid pressure and exhaust lines 38 and 3| totake up the backlash in the proper direction. During the return drive tothe left, the solenoidSVCR is deenergized; and they solenoid SVCL is mergized to actuate the valve28 into the other position, thereby reversingthe connections to the cylinder lines 26 and 21 so as to take up thebacklash in the opposite direction.

The work head drive The drive for the work head 8 is automaticallyadjustable to vary the speed of spindle translation and rotation inaccordance with the nature of the work being done at different points inthe machine cycle; and comprises a reversible hydraulic motor 32 ,of therotary type having a constant displacement at any given speed. A pulley33 on the shaft 34 of the motor 32 is connected through a belt 35 to apulley 36 on the rear outer end of the power inlet shaft 18 of thetoolhead 8 (Fig. 2).

The motor 32 has fluid supp lines 31 and 38* connected in a hydraulictransmission system (Fig. 13) to receive fluid under pressure, subjectto control by a direction valve 39and an-orifice selection valve 40,from the pressure line 4| of a variable delivery pump 42 driven by anelectric motor 43. The pump 42 has an inlet line 44 taking fluid from areservoiror sump 45 in thebase of the machine, and its displacement oroutput is subject to variation in response to the pressure in a controlline 48 adapted tobe connected to the pressure line 4| by the valve 39when adjusted to effect traverse of the table 3.

The direction valve.39 has an intermediate or stop position, andopposite end positions to effect reversible operationof the motor 32,andin said opposite end positions serves to-direct fluid discharging fromthe motor 32 respectively to one or the other of two exhaust lines 41and 48. The exhaust line 41 leads to the inlet ofthe orifice selectionvalve 4|| which has three positions of adjustment to direct the exhaustfluid respec tively" to three orifice lines 49, 58 and 5| duringforwardfeed operation. A plurality of independently adjustablerestricted orifices; 52, 53 and 54 for feed control are respectivelyinterposed in the lines "49 58 and 5|, and discharge to a drain line 56returning to the reservoir 45. An adjustable restricted oriflce'55 isconnect-edto receive fluid f romthe exhaust line 48during rapid traversereturn and also discharges to the drain to the respective inlet andoutlet lines 31, 38, 4|,

lines 41 to 5|. Each ofthe orifices isprovided with an indicator dial onthe front of the block The direction valve 39 comprises a horizontalbore opening crosswisethrough the block 51 and having a valve sleeve 58fixed therein. The sleeve 1 58 is formed with longitudinally spaced setsoi .radial ports 59, 60, 5|,, B2 and 63, opening to the inner periphery,and connected respectivelyto the coredpassages 48,31,4l, 38 and 41. Twospaced sets of'restricted ports 84 and B5 are also formed "in the valvesleeve 58,and are connected in parallel through fixed orificeplugs 68 tothe cored control passagellfi'.

Avalve plunger 61 of the spool type is reciprocable in the valve sleeve58 with a snug sliding fit, and is formed with end lands 68 and G9, andanintermediate land 10 separated by peripheral grooves 1| and 12. i i

The orifice selection valve 48 is generally similar, in construction tothe direction valve 39, and

comprises a horizontal bore opening crosswise through the block 51 inparallel verticalspaced relation to the bore of the direction valve. Avalve grooves83 and 84 for selectively blocking and line 56. Theselective controlorifices 52j -53, 54

and 55 are, therefore, adapted-to 'bedndividually connecting the valveports in difierent positions of adjustment of the valve.

The direction valve 39 has three positions, namely, an intermediate stopposition and opposite end positions. Normally, the valve is biased byspring pressure into the intermediate stop position. A valve stem 85projects from one end of the valvemember 51 for connection to suitableactuating means, and has a rod 86 of reduced diameter extending axiallythrough the valve member;

A nut 81 is threaded onto the free end of the rod 86to clamp the valvemember rigidly to the stem 85. The stem 85 extends through a bore 88 ina bracket 89 mounted on one end of the panel block 51, and is formedwith a peripheral enlargement defining a shoulder 58 in opposed ax--ially spaced relation to theadjacent end of the valve member 81.'Slidably disposed on the valve stem within the bore 88 are twofiangedrings 9|1and92 urged apart by a coiled compression spring 83.

The pump 42 is substantially e that shown in an application for unitea-state -rett r Patent 1 i by Max Mathys, Serial No. 379,211, filedFebruary 17, 1941.

In operation, when the stem 85 is not externally actuated, the spring 93will maintain the rings 9| and 92 in spaced relation respectivelyagainst the end of the valve member 61 and the shoulder 90 and alsoagainst the end of the valve sleeve 58 and the outer wall of the bore88. Upon actuation of the stem 85 outwardly, the ring 92 will be movedto the left by the valve member 61 to compress the spring 93. Uponactuation of the stem 85 inwardly, the ring 9| will be moved by theshoulder 90 to compress the spring 93. Upon releasing the valve stem 85in either instance, the spring 93 will expand to return the valve member61 to intermediate position.

The orifice selection valve 40 also has three positions, and normallythe valve member I9 is biased by a compression spring 94 into theintermediate position. The means coacting with the spring 94 are thesame in construction as in the case of the direction valve 39 and,hence, need not be again described. It is suflicient to state that thevalve member I9 has an axial stem 95 projecting from one end through abracket 96 for connection to suitable actuating means.

The direction valve 39 and the orifice selection valve 40 are shiftableinto their opposite end positions respectively by solenoids SVFW andSVREV and, solenoids SVI and SV2 which are mounted on the rear ofthetblock 51 and are connected in the electrical control circuits of ito translate the work table 3, for example at a the machine. Thesolenoids SVFW and SVREV forthe direction valve 39 are disposed in endalinement, and have a core 9! extending axially therethrough andprovided on opposite ends with suitable heads 98 for limiting the extentof movement. One end of the core 91 is pivotally connected through aclevis99 to one end of a lever I00 in turn pivotally connectedintermediate its ends at IN on the bracket 89. The other end of thelever I00 is pivotally connected through two parallel links I02 in turnpivotally connected to the flattened outer end of the valve stem 05.

When both solenoids SVFW and SVREV are deenergized, the spring 93 willlocate the valve member 61 in its intermediate or stop position in whichthe lines 3! and 38, leading toopposite sides of the motor 32, areinterconnected and con 'nected to the pressure and control lines 4| and46, and are blocked from the exhaust lines 41 and 48, thereby adjustingthe pump 42 for minimum displacement sufficient to maintain a deliverypressure.

When the solenoid SVFW alone is energized, the valve member 61 isshifted out of intermediate position to the right so as to connect thepressure port 6| to the motor line 31 and to connect the other motorline 38 to the exhaust passage 41. Upon deenergization of the solenoidSVFW and energization of the solenoid SVREV, the valve member 61 isshifted from the intermediate position to the left into the opposite endposition to connect the motor lines 38' and 31, respectively, to thepressure line 4| and the exhaust line 48.

Th solenoids SVI and SV2 for the orifice selection valve 40 are disposedin end alinement on the rear of the panel block 51, and over thesolenoids for the direction valve 39, and have a core I93 operativelyconnected to the stem 95 in the same manner as in the case of the valve39. Upon energization of the solenoid SVI, the valve member 19 isshifted out of intermediate position to the right so as to connect theexhaust passage 41 .to the passage 5| for rough slow feeding speedduring each roughing pass, a faster feeding speed during each finishingpass, a speed slower than that-for rough grindin during the grinding ofthe incomplete end thread convolution, and a high rapid traverse speedduring each free return stroke.

Tool head The tool head 6 comprises a wheel slide I04 which is mounteddirectly on the rearward base extension 4 for reciprocation along theways 5 transversely of the work axis. The grinding wheel spindle l issuitably supported on the forward end of the slide I04 for angularadjustment in accordance with the lead angle of the thread, and isadapted to be driven through a belt 106 by an electric motor I01. I

When an incomplete end thread convolution is to be removed from theleading end of the workpiece W, a second grinding wheel G" is fixed onthe spindle 'I in axially spaced relation to the grinding wheel G totake a grinding cut on the convolution at the end of each roughing passand each finish pass. The method of removing the incomplete threadconvolution is more fully disclosed in a copending application forUnited States Letters Patent by Gilbert Stewart, Serial No. 426,112,filed January 9, 1942, to which reference may be had for a more detailedunderstanding. During the end portion of each grinding pass, thesolenoids SVI and SV2 are both energized to reduce the speed of thetable 3.

Slidably mounted on therear end portion of the wheel slide I04 ontransverse'ways I08 is a dresser slide I09 (see Fig. 8). A suitabledressing device IIO having one or more dressing tools I I I is mountedon the slide I09 and is adapted to be reversibly driven in any positionof the slide by an electric motor II2 through a flexible shaft II3 totraverse the tools across the cutting contour of the wheel G.

The wheel slide I04 is adapted to be translated hydraulically eitherforwardly into an operative grinding position for each grinding pass, orrearwardly into an idle or dressing position for each return stroke ofthe table 3. The means for this purpose includes a leadscrew II4 whichis rotatably anchored against relative endwise movement in the lowerportion of the wheel slide I04, and which is normally non-rotatable butoperated as hereinafter described to impart a compensating forward feedto the slide for each dresser feed. The forward end of the lead screw II4 is in threaded engagement with a nut II5 fixed in the rear end of acylindrical plunger or stop member IIB slidably disposed for independentlongitudinal adjustment in a bore II! in the wheel slide I04, andconstrained against rotation therein by a spline key II8. A stop bolt H9is adjustably threaded into the forward end of the stop plunger I I 6,and is arranged for abutting engagement with the rear end of a coactingstop plunger or member I20. A coiled tension constantly in endabutmentwith the stop member I20.

The stop member I20 issiidably disposed in a sleeve bearing I22 on thebase extension 4, and is held therein against rotation byrneans of aspline key I23. Fixed inthe forward end of the stop member I20 is a feednut I24 in threaded enaurfm.

gagement with the cross feed screw I25. Thev forward end of the"feedscrew I25 has a shaft I26 which is connected to the cross feedmechanism I2, and which constitutes an anchor ad-- justable individuallyor conjointly by the retract mechanism I3 and the taper mechanism I4 tocontrol theposition of the wheel slide I04 independently of the crossfeed. 1

I The retract mechanism I3 and the tapermechanism I4 jointly control theaxial position of the cross feed screw I25 through the medium of a leverI21. with a yoke I28 engagingtrunnlons I23 on an end thrust bearing I30rotatably secured on the feed screw I25. The other'end-of the lever I21is similarlyfformed with a yoke I3I engaging trunnions I32 on an endthrust bearing I33 rotatably secured to one end of a slidable plungerI34 forming part of the taper 'mechanism I4. The .trunnions I32constitute a fulcrum about which the lever I 21 isoscillated by theretract mechanism. I3 to shift the cross feed screw I25 axially inforward and reverse directions. Inits preferred form, the retractmechanism I3 in? cludes a'hydraulic actuator I35 comprising a cylinderI36 fixed in the base I, and a piston I31 reciprocable inthe cylinderand having a rod One end ofthelever I21 is formed andis formed initsinner end witha longitudinal .diametrical slotl54receiving thesegment III which engages the outer end of the slot to complete theoperative connection between the plunger I34 and the pin I41. 5 I

Upon movement of the pin I41 along the sine bar I43, the operation .ofthe plunger I34 will be determined by the angle of the bar. If the baris horizontaLnotaper movement will result; If the baris inclined, theplunger I34 will be shifted infthe course of the table movement asdetermined by the angle of adjustment to oscillate the lever I21 aboutthe fulcrum I39, andthereb'y adjust the grinding wheel G transverselyofthe work axis in accordance with the desired work I taper. I

Means is provided for disabling the taper r mechanism I4, and inthepresent instance this means comprises a slide I55 mounted in thehousing I49 for adjustment longitudinally of the plunger I34, and havinga stop lug I56 projecting into the lower opening of theslot I54. An adjusting screw I51 extends rotatably through the front wall of thehousing I49 into threaded engagement with the slide I55, and uponadjustment serves'to change the position of thelug 1 I56 and I thepermissibierange of movement of the plunger I34. If the slide I55 isadjusted into its outer-- most position (Fig. 6) it serves to holdtheplunger I34 inidle position out of functional association with thesine bar I43 and hence disables the taper mechanism. In this event, thetrun- .I38 pivotally-connectedat I39 tothe lever I21 intermediate itsends. The cylinder has two fluid lines I40and I4I adapted tobe connectedby a direction ,valve I42 reversibly to the pressure line 30 and exhaustline 3|. The valve I42 is of the two-position type, and is normallybiasedinto oneend position to-direct fluidinto the line I so as toeffect movement of the wheel slide I04 forwardly into its operativegrinding position.) A s nions I32 constitute a fixed instead ofshiftablefulcrum about which the lever I21 is adapted for oscillation by theretractmechanism I3. I

f Grinding wheel dressing 1 Prior to each dressing operation, anincrmental dresser feed. is imparted to the dresser slide; I09 to shiftthe dressing tools III toward the periphery of the grinding wheel G, andsub-' stantially at the end of each feed increment, a

limit switch LS5 is actuated to institute operationof the dressingdevice 0. Thereupon, the dressing device IIO is-operated through'a cycle1 of forward and return dressing strokes under the solenoid SVR isoperable upon being energized to shift the valve I42 into its other endposition to direct fluid into the line I40 so as to retract the wheelslide I04 intoits idle or dressing position. The solenoid SVR isconnected in the 'electric'circuits for the machine, and is energiied,as an incident to each reversal of the work table 3, during each returnstrokeand deenergized during each grinding pass. Preferably, a throttleorifice I40 is inserted in the line I40. to control thespeed of theactuator I35.

The taper mechanism I4 comprisesia sine bar control of two limitswitches LSDF and LSDR.

The dresser feed mechanism includes a feed screw I58 rotatably anchoredagainst endwise movement in the'wheel slide I04 andextending' is flxedfor rotation with thepinion Iii, and

' I43 which isinounted for angularadiustment about a pivot I44 at oneend on the front of the work table 3. The other end ofthebar I43 isguided by a pin and slot connection I45; and is adapted to be secured indifferent positions of adjustmentby means of a locating clamp block I46.A vertical follower pin I41 is reciprocable in a boss I46 on'a housingI49 'securedto the meshes with a spiral gear I63 fixed on a cross.

shaft I64 extendingthrough a sleeve I to one side of the base extension4. The shaft I64 is journaled at opposite ends in the sleeve I65, andextends therefrom through a housing I66. A

suitablehand wheel I61 is secured to the outer front ofa mounting plateI50bolted to the front .wall of the base I. The-upper end of the pinI41. is arranged for'wiping engagement with; the

lower edge of the sine bar I43 in the course. of the table translation.The lower endoi the pin I41 engages one side of a bell crank or segmentI5I pivotally mounted on a shaft I52 within the housing I49. The plungerI34 extends slidably through a bushing I53 into the housing I49.

end of the shaft I64 and affords means for effecting manual operation ofthe dresser feed.

, The housing I66 encloses suitable drive means for automaticallyoperating the "dresser feed shaft I I64. In the present instance-thedrive means comprises a ratchet- I66 keyed to the shaft I64,

and a gravity pawl I63 adaptedforengagement with theratchet and mountedon the end of a pawl carrier or arm I10 oscillatory about the shaft. Thefree 'end of the pawl carrier I10 is formed with a gear segment Illoperable by a hydraulic actuator I12 on the housing. I66. In the presentinstance; the actuator comprlses a 11 plunger I13 reciprocable in acylinder I14 and formed in one side intermediate its ends with alongitudinal gear rack I1I' meshing with the segment I'II. Thus,movement of the plunger I13 in one direction will advance the pawl I69in a feed stroke to impart rotation to the ratchet I68, and movement ofthe plunger in the reverse direction will oscillate the pawl in an idlereturn stroke.

The cylinder I14 of the hydraulic actuator I12 has twofluid supply linesI15 and I16 opening thereto at opposite ends of the plunger I13, andadapted to be connected by a direction valve I11 reversibly to ,thepressure line 30 and exhaust line ill, The, valve I11 is of thetwo-position type, and is normally biased into one end posit-ion todirect fluid into the line I15 so as to effect oscillation of the pawlI69 in its free return stroke. A solenoid SVD is operable upon beingenergized to'shift the valve I11 into its other end position to directfluid into the line I16 so as to oscillate the pawl I69 through itsfeeding stroke. The solenoid SVD is connected in the electric circuitsforthe machine, and is adapted to be energized at predetermined pointsin the machine cycle, for example after every two grinding passes underthe control of an electric counter having an operating coil or relay Band aclutch coil or relay, A.

The extent of the dresser feed movement is adjustably controlled by acam I18 arranged to lift the pawl I69 out of engagement with the ratchetI68 to terminate the feed. Substantially at the end of the dresser feed,the carrier I10 actuates a limit switch LS to initiate the cyclicoperation of the dressing mechanism I5.

Upon each dresser feed, a cross feed increment of the same extent isimparted simultaneously to the wheel slide I04 so as to compensate forthe reduction in the diameter of the grinding wheel G resulting from theremoval ofstock in the dressing operation. The compensatory cross feeddrive comprises a' gear I19 on the dresser feed screw I58, an idler gearI80 meshing with the gear I19. and a gear I 8i on the compensatory feedscrew I I4 and meshing with the gear I80. It will ,be seen that uponrotation of the dresser feed screw I58, rotation will be imparted to thecompensation cross feed screw I I4 so as to retract the rear stop memberH6, and thereby cause the spring I2I.to advance the grinding wheel Gthrough a like distance towards the work axis.

Cross feed mechanism The cross feed mechanism I2 for the grinding wheelG is operable to adiust, the position of the forward stop member I20 byrotating. the cross feed screw I25, and thereby to control the sizesetting of the grinding wheel G in relation to the workpiece W. Themechanism is manually operable to adjust the grinding wheel G intoinitial setting as required by the-diameter of a particular workpiece 'Wto be ground, and during the machine cycle is automatically operable toimpart a cross feed increment of predetermined depth once for eachgrinding pass, after the initial grinding pass, of the work head 8 untilthe thread is ground to final size or depth.

In its preferred form, the cross feed mechanism I2 comprises a bodybracket I82 integral with,the mounting plate I50, and formed with a boreI83 coaxialwith thefeed screw I25. A fixed bushing I84 is securedin thebore I83, and projects forwardly therefrom. Rotatably disposed in thebushing I84 is a tubular sleeve I85 which 12 constitutes the terminal oroutlet shaft of the cross feed mechanism I2, and in which the screwshaft I26 is axially splined for joint rotary drive and independentaxial movement.

The forward projecting end of the tubular shaft I is formed with axiallyspaced peripheral flanges I86rotatably supporting a hub member I81.Preferably. a bearing sleeve I88 is fixed in the. hub member I81, andengages the flanges I86 with a snug rotary fit. The forward end of thehub member I81 is formed integral with a circular plate I89 having aforwardly projecting annular flange I90. Rigidly secured in coaxialrelation to the flange I90 is a hand wheel I9I provided with a suitablehand grip I92 for effecting a manual cross feed. I

Adis'engageable speed-reduction gear drive is provided between the handwheel I9I and 'the shaft I85. In its preferred form, this gear driveincludes a large gear I93 bolted to the forward end of the shaft I85 incoaxial relation therewith. The gear I93 meshes with one end of anelongated axially shiftable pinion I94. The other end of the pinion I94is slidable in and meshes with an internal gear I95 which is journaledin the inner face of the hand wheel I9I, and is integral with anexternal gear I96. An idler gear I91 rotatably mounted on the inner faceof the hand wheel I 9i meshes with the gear I96. Meshing with the gearI91 is a gear I98 on a shaft (99 extending axially through the handwheel I9I, and provided on the outer end with a hand lever 200. A springactuated detent 20I is carried by the free end of the hand lever 200,and is adapted when released to engage selectively in any one of anannular series of holes 202 provided at the front of the hand wheel I9Iconcentrically about the shaft I99.

.The gear I94 is provided on one end with an axial pin 203 adapted forengagement in a recess 204 within the plate I89, and is provided on theother end with a hand knob 205 whereby it may be retracted axially outof meshing engagement with the large gear I93. A spring actuated detent206 serves to hold the gear I94 releasably in either position ofadjustment. When the gear I 94 is disengaged from the gear I93, the handwheel I9I can be rotated independently of the shaft I85 as required forcoarse adjustment relative to a fixed reference point or pointer 240.Assuming the gear I94 to be in mesh with the gear I93, when the detent20I is disengaged from the holes 202, the lever 200 may be manuallyrevolved to effect a fine adjustment of the hand wheel I9I relative tothe shaft I85, the gears I98, I91, I86 and I95 acting to roll the gearI94 about the gear I93. If the hand wheel I9I is held against rotation,operation of the lever 200 will rotate the gear I93 to adjust the-screwI25. By these operations, the screw I25 may be adjusted into correctsize position, with the wheel I9I registering with a zero point. Whenthe detent 20I is engaged in any one of the holes 202, the hand wheel ISi is locked through the gear train to the shaft I85 for direct rotationtherewith.

A pawl and ratchet mechanism is provided for imparting an incrementalautomatic feed adjustment to the shaft I85, and preferably comprises aratchet 201 rigidly secured to the rear end of the hub member I81. Apawl carrier 208 is mounted for oscillation on the outer end of thebushing I84, and is confined in axial position between the plate I50 andthe end of the hub member I81. Pivotally mounted by a pin 209 in the endof the pawl carrier 208 is a pawl 2| 0 adapted for en- 13 I gagementwith the periphery of the ratchet 201. A spring detent 2II coacts withthe pin 2ll3-to maintain the pawl 2l0 either in operative position toengage the ratchet 201 or in a lifted position out of engagement withthe ratchet.

The carrier 208 is formed with'a gear segment 2I2 which meshes with apinion 2I3 on the forward end of the shaft 2H rotatablydisposed within abore 2I5 in the body bracket I82. A pin ion 2IE on the rear end of theshaft 2 meshes with a gearrack 2 I! on one-side of a longitudinal rackbar2l8 reciprocable in andprojecting from a transverse bore H9 in thebody bracket I82.

The outer end of the rack bar 2I8 is pivotally connected at22llthroughaaconnected rod 22I to a crank 222 operable by a hydraulicaetuator 223. In the present instance, the hydraulic actua tor 223 ismounted on the front of themachine base I, and comprises a piston 22,4reciprocable within a cylinder 225 and connected through a cross feed ofthe wheel slide I041 I ,Hy dfou lic circuits 1 y r V The variousoperating elementsof the hydraulic circuits have sheen describedinwtheforegoing It is to be noted that one portionof the circuit provides ahydraulicldrive for the work table 3 and spindle III.; This portionreceives fluid under full pressurefrom the pump-42 through the line II.*A relief. valve. 250 is "connected to the line II to discharge excessfluid at a given pressure through a bypass linel and the exhaust line 153 to the sump .45. The other portion of the circuit serves varioushydraulic actuators of the machine proper, viz., the retractyactuator"I35,

rack 228 andpinio'n 221 to the crank 222, The

cylinder 225 has two fluid lines 228 and 229 adapted to be connected bya direction valve 230 reversibly to the pressure line and exhaustJine3|. The direction valve 230 is of the two-posithe dresser feed actuatorI12 and the cross feed aetuator223, and receives fluid at a constant lowpressure from the pumpiline 4i through apl'essure reducing valve 252 tothe line 30.

tion type, and is normally biased into one end I position to directfluid into the line 228 so as to effect movement of the pawl 2H! in areturn stroke. A solenoid SVD is operable upon being energized to shiftthe valve 230 into. its other end position to direct fluid into the line229 so as to move the pawl 2I0 in a feedin stroke. At the end of thefeeding stroke, a cam 23I on the crank 222 acts to open a l mit switchLSF. to interrupt the circuit for the solenoid SVD.

The amount of each cross feed increment is adjustable by varying theeffective strok of the pawl 2| II. .Themeans for this purpose includes arotary shield 232, overlying the periphery of the ratchet 201, andadapted to lift the pawl 2 III outof engagement withthe ratchet teethafter i a predeterm ned extentof pawl movement. The shield 232 isrotatable about a ring 233fwhich v nzircles the hub member I81, andwhich is rigidly bolted to thebody housing I82 to secure the cross feedmechanism I2in mounted position. 'A feather 234 on the hous ng I82extends through a slot 235 in the shield .232 into a groove 236 in thering 233. andserves as an additional means for securing the parts inassembled relation. 'A

hand knob 23'! is secured to the shield 232 by means of a bolt238extending through a periph era! slot 239 m the ring 233..and affordsmeans for adjusting the shield relative to the pawl 2H1.

Enoircling the ring233 and rigidly secured there to outwardly from theshield 2321s an annular Electrical control circuits and operationCurrent is supplied for all or the various moxtors, excepting thegrinding wheel motor I01,

from three main supply lines Li, L2,*La, which are adaptedto beconnectedto asuitable source of three-phasealternating current by a maindis connect switch S1. Suitable lower voltage current forthe controlcircuits proper is derived from a step-down transformer 253 having aprimary winding connected across the supply lines Li, L3

and a secondary winding, with a line Liconnected' to one terminal and alineLs connected to the other terminal. A line L6 is adaptedto beconnected to the leadLs upon closing a normally open start switch S2 forthe hydraulicfmotor 43. Accordingly, the various electrical controldevices of the system may be energized by connecting them acrosseitherthe lines L4 and L5 or L4 and La The hydraulic pump motor 43 and alubrication pump motor-254 are adaptedto be 'connected. in parallelto'the lines L1, L2 and La through. a set of normally open switchcontacts H? controlled by a relay. H. To start the pump. motors I43 and25-I t he start switch S2 is closed,

thereby completing a circuit forthe relay H across the lines L4 and L5,the circuit being from L4 through the relay H, a series of overload andpro- 'tective relays, a normally closed-master stop disk 239 whichinterflts rotatably withthe outer edge of the plate I89 and supports thepo nter 240 for indicating the adjustment of the hand wheel I9I. r Thehand wheel I9I controls a limit switch LS SI for initiating the end orthe machine cycle .when the cross feed reaches final size. The switchLSSI has an arm 2 connected through a link 242 to an ans-243; on 9.shaft 244 journaled in the base I. Secured to the forward end of theshaft 244 is an arm 2.45 in which a. finger246 is adustablypivoted forswinging movement into or out of operative position. A fixed dog 24 1 issecured to the hand wheel IS, and is arranged to engage one side of thefinger-248 to actuate the switch LSSI at the end of the cross feed. Asecond dog 248 is adjustably secured in a peripheral T-slot 249 inthewheel I9I, and is adapted to be'brought into engagement with the otherswitch Saand the switch S2 to the line L5. Energization of the relay Hcloses the contacts H to set the pump motors and 254 in operation, andalso closes sealing contacts H to establish a holdingcircuit around thestarting switch S2;

When contacts H are closed, lines L5 and Le are connected to conditionthe circuits forconnecting the cycle control devices across the lines Liand Le.

Closing of the switch S2 also establishes a circuit across the lines L4and L5 for the solenoid SVI through normallylclosed contacts CRSI' and anormally closed limit switch LSI3. Aparallel circuit for the solenoidSV2 is interrupted at this time by normally open contacts CRBIThesolenoid SVI upon being energized serves to actuate the valve 40 todirect the discharge of the hy-' drauiic motor 42 through the adjustablyrestricted orifice 54 set to control the table speed for rough grinding.In the event that the end thread convolution isnot. to be removed, thesolenoidSVI and the limit switch ILSI3 may be removed from the circuit.

including a closed limit switch LSSI.

A circuit is also established across .the lines L4 and L5 for a relayCR1 and the solenoid SVCR through a limit switch LSTA upon movementofthe table 3 to the right. The solenoid SVCR actuates the valve28 toeffect operation of the actuator 23 in a direction to provide a backlashcompensation to the right. Upon reversal of the switch LSTA at the endof the table travel to the right, the circuit for the relay CR1 and thesolenoid SVCR is interrupted, and a parallel circuit is established fora relay CR9-and the solenoid SVCL. As a result, the valve 28 is reversedto effect a backlash compensation to the left.

The grinding wheel motor I01 is adapted to be connected across lines L1and La connected to a source of direct current, and comprises a seriesfield 255, a shunt field 256, and'a starter 251 having an operating coilwith a timer (not shown). The field 256 is connected in series with twoadjustable resistances 258 and 259 across the lines L7 and La. 1 J

To start the wheel motor I01, and also a coolant pump motor 260 andrefrigeration unit motor 26I, a hand switch S4 is closed to complete acircuit for relays C and REFR through a stop switch S5. The relay Ccloses sealing contacts C across the switch S4, contacts C to complete acircuit through the operating coil OP, and contacts C to connect themotor 260 to the lines L1, L2 and L3. Upon energizing the coil OP,contacts 0P OP and OP of the starter 251 are closed successively tostart the grinding wheel motor I0I. At this time, the resistance 259 isshunted out through the contacts CR3I so that the motor I01 is operatingat a relatively low speed adapted for rough grinding. The coil REFRcloses contacts REFR to connect the motor 254 to the lines L1, L2, La.Consequently, closing of the switch S4 ifects operation of all threemotors I01, 254 and 260.

Various selector switches are provided for conditioning the circuit toobtain a particular Inachine cycle. Switch Se is adjustable to controlthe cycle for either hand operation, single cut operation or automaticoperation, and in the position shown closes all of its contacts toprovide for automatic operation. Switch S1 is adjustable to conditionthe counter for counting table strokes or workpieces, and as shown,provides for the counting of strokes, for example, four strokesincluding two grinding passes. Switches Se and S9, in parallel andlocated at the front and rear of the machine, are adjustable to efiectcontinuous wheel dressing or intermittent dressing, or to disable thedressing mechanism, and as shown, provide for intermittent dressing.

At the start of the cycle, relays TRI, CRIO, CR3 and'CRI5, and solenoidSVR are energized, and the lamp RED is illuminated. The solenoid SVRmaintains the wheel slide I04 in'retracted position.

The machine cycle is started by actuating a start cycle switch S10 toclose a circuit across the lines L4 and L through a relay'CRI, thiscircuit Excitation of the relay CRI closes sealing contacts CRI acrossswitch S10, and contacts CRI' to complete a circuit for a coolant valvesolenoid-262 across lines LI and L3. The circuit for the relay CRI willremain closed unless a stop cycle switch $11 or the-masterstop switch S3is opened, or until the limit switch LSSI is opened at the end of thewheel cross feed.

The relay CRI also opens contacts CRI to noid SVR causes the valve 42 toshift so as to effect advance of the grinding wheel G into operativegrinding position.

Upon release of the start cycle switch S10, and after a time delay, therelay TRI causes closing of contacts TRI to complete a circuit forrelays CR4 and CR8 and solenoid SVFW. Relay CR4 closes sealing contactsCR4 to establish a holding circuit. Solenoid SVFW shifts the valve 39 toeffect movement of the work table 3 in a forward rough grinding pass.

The relay B of the counter and the clutch relay A are connected acrossthe lines L4 and La, and hence are in a state of energization. When therelay CR4 is energized, it opens contacts CR4 to interrupt the circuitand register a pass on the counter. Since three passes of the precedingcycle were already registered thereon, the counter closes contacts 263to complete a circuit for relay CRB which closes sealing contacts CR6.The relay CR6 also closes contacts CR6 in the circuit for the dresserfeed solenoid SVD, but this circuit is not completed since contacts CR4are open.

Near the end of the first roughing pass, the

table 3 opens the limit switch LSI3 to deenergize the solenoid SVI, andthereby reduces the feeding speed for grinding the incomplete end threadconvolution by the grinding wheel G.

At the end of the first roughing pass, the table 3 actuates the switchLSTA to break the circuit for the relay CR1 and solenoid SVCR and tomake the circuit for the relay CR9 and solenoid SVCL.

Relay CR9 closes contacts CR9 to close again the circuit for the relayCRIO and solenoid SVR. The relay CRIO closes contacts CRI0 to completethe circuit for the solenoid SVD for effecting the dresser feed, and thesolenoid SVR effects retraction of the grinding wheel G. The relay CRIOalso closes contacts CRIII to complete the circuit through contacts CR9and CR9 for the solenoid SVREV and relay CR5 to effect free returnmovement of the table 3 to the left.

Operation of the dressing mechanism I5 continues during the wheelretract movement and the table return movement. At the conclusion 'ofthe dresser feed, the limit switch LS5 is closed momentarily to completethe circuit for dresser relay DF, which closes sealing contacts DF andopens interlock contacts DF'. Relay DF also closes contacts DF tocomplete a circuit for relay CR32 through contacts CR6 Relay CR32 closescontacts CR32 to shunt out the resistances 258 and 259 so as to rotatethe grinding wheel motor I01 at a slow dressing speed.

The dresser IIO now operates forwardly, and closes the limit switch LSDRto prepare the circuit for relay DR. At the end of the forward dressermovement, the limit switch LSDE is opened, and upon resultant closing ofcontacts DF', the dresser relay DR'is energized, opening interlockcontacts DR and closing conacts DR The dresser now operates in thereverse'direction during which the switch LSDF is closed, and at the endof which the limit switch LSDR is again opened to terminate the dresseroperation.

When the contacts DR are opened at the end of the forward dressingstroke, the relay CR6 is deenergized, but the circuit for the relay CR32is maintained by the contacts DR At the end of the dresser operation,the contacts DR open to break the circuit for the relay CR32. As a re-

